This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present disclosure. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present disclosure. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
Field of the Invention
The present disclosure relates to the field of hydrocarbon recovery operations. More specifically, the present invention relates to a system for hanging a string of production tubing in a wellbore, while allowing an operator access to the wellbore from the surface. The invention also relates to a method of accessing a wellbore through a tubing hanger assembly using a novel adapter.
Technology in the Field of the Invention
In the drilling of oil and gas wells, a wellbore is formed using a drill bit that is urged downwardly at a lower end of a drill string. The drill bit is rotated while force is applied through the drill string and against the rock face of the formation being drilled. After drilling to a predetermined depth, the drill string and bit are removed and the wellbore is lined with a string of casing.
It is common to place several strings of casing having progressively smaller outer diameters into the wellbore. In this respect, the process of drilling and then cementing progressively smaller strings of casing is repeated several times until the well has reached total depth. The final string of casing, referred to as a production casing, is typically cemented into place.
As part of the completion process, the production casing is perforated at a desired level. Alternatively, a sand screen may be employed at a lowest depth in the event of an open hole completion. Either option provides fluid communication between the wellbore and a selected zone in a formation. In addition, production equipment such as a string of production tubing, a packer and a pump may be installed within the wellbore.
During completion, a wellhead is installed at the surface. Fluid gathering and processing equipment such as pipes, valves and separators are also provided. Production operations may then commence.
In typical land-based production operations, the wellhead includes a tubing head and a tubing hanger. The tubing head seals the wellbore at the surface while the tubing hanger serves to gravitationally support the long string of production tubing. The tubing string extends down from the tubing hanger proximate to a first pay zone.
During the production process, the production tubing may experience thermal expansion over time. This is due to the presence of warm production fluids being produced up through the pipe and to the surface. To offset the anticipated expansion, it is known to place the production tubing under some degree of tension when the well is completed. This will maintain the production tubing in a linear state even while the pipe string relaxes in response to thermal expansion. Thus, even when the production tubing expands over time, the tubing does not buckle within the wellbore. This is of particular benefit when the wellbore is being rod pumped, as pre-tensioning minimizes frictional contact between the rod string and the surrounding production tubing during pumping.
In connection with hanging the tubing in the wellbore, it is sometimes desirable to run an electric line to provide power to a resistive heater or to an electric submersible pump (or “ESP”) downhole. U.S. Pat. No. 6,688,386 entitled “Tubing Hanger and Adapter Assembly” provides one wellhead arrangement for running a power cable at the surface through a tubing hanger system. Such a wellhead arrangement uses an adapter above the tubing head to accommodate and to isolate the electric line. However, this and other known wellhead assemblies have limitations concerning the alignment of ports drilled in the adapter with through-openings located in the top flange of the tubing head.
In connection with hanging the tubing in the wellbore, it is further desirable to provide a fluid supply line into the well. However, existing tubing tensioning arrangements generally prevent the use of the somewhat non-ductile fluid supply line that will descend through and below the tubing hanger. Moreover, known tubing hangers generally require that the tubing string be rotated or turned five or more times in connection with setting the tubing anchor downhole and locking the tubing hanger at the surface. Typical stainless steel chemical injection lines cannot tolerate the stress and tension induced by the produced torque, nor can they be “snaked” through access ports that are not perfectly aligned.
Accordingly, a need exists for a tubing hanger assembly that enables hanging tubing from a tubing head at the surface with less than one complete rotation of the production string during hanging. Further, a need exists for an improved tubing hanging system that is able to accommodate a chemical injection line without twisting the metal line as it enters the wellhead and travels downhole. Still further, a need exists for an adapter that is part of the wellhead that enables a communications line to be run through the tubing hanger and down the wellbore, and that connects to survey equipment downhole.